Question about EA-81 Subaru

Tina

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Is the vacuum on the vacuum advanced distributor supposed to be hookup?
I know on a car it is but on a gyro? because mine is not, please help.
 

Tina

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okay, wouldn't it make more power if I hooked it up? I have a place on my carb to hook it to. Like it sould be on a car, if no then why not?
 

mceagle

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If you run it disconnected you cannot set the ignition timing to factory specs. This is not a problem but it means you have to set the timing with a light at 3,000rpm or above, to 28* to 30*. It is actually more accurate to do it this way because you are eliminating inaccuraces due to wear, variations in vacuum and (as is often the case) mismatched components.
The only problem you may encounter is too much static advance for hand starting - in which case you will have to reconnect the vacuum advance to get a lower base setting.
 

M. Pearce

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Tina,
On full out race engines the guys dump vacuume advance systems altogether. I my scca VW's I have converted them to cintrifugle advance distributors. WE just do this because of the poor vacuum we get with HiPo race intake systems that are quite known for radical vacuum variances. If you set your timing and then plug her back up it might give you too much advance. Too much advance over a long period, thirty minutes to an hour straight run might cause pre detination problems. Predetination is simple to find. After your engine quits just pull the head, you will find a nice little hole melted through your piston. It also causes temperary engine siezure in two stroke engines. This is why race engines go with forged pistons that can handle more heat with less thermal expansion. A more heat handling piston relates to an engine that can run longer with a more advanced timming setttings for more overall power output. Go a centrifugle advance distributor if you can, it relates to more control, more power when you need it and more easy to troubleshoot later on.
 

Chopper Reid

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Tina, take Tims advice, he has had more to do with EA 81's than most guys and he has built and maintained plenty of gyros. My old EA 81 was fitted up like he said and it worked just fine !!
 

GyroRon

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Hell, let em hook up the line and if the gyro makes less power or is harder or easier to start they will find out on their own. The fact that nearly everyone I know that has used the EA-81 engine disconnects the advance and plugs off the manifold, and the fact that nearly all of them get rid of the points and put in a aftermarket electronic ignition.... well these people don't know what the heck they are doing.... Right?

Now I have seen with my own eyes, the EA-81 is easier to start if you leave the points ignition in it instead of the electronic ignition.
 

Vance

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Hello Tina,

This is an important question properly asked. Finding your level of understanding is what is causing the confusion.

In my opinion, a vacuum advance is there to advance the ignition at hi vacume, low throttle opening, for better fuel milage. It usualy advances the timing well past best power. In an aircraft not much time is spent at low power, high vacuum, so there is not much value in the device.

Tim is trying to show you how to work around the timing issue because the factory timing is set with the vacuum advancing the timing.

The hose should be pluged on the manifold end as it acts as a leak in the intake system and will often cause low speed mixture problems.

Please keep asking your good questions and pushing back when you don't understand the answers you recieve. You are never the only one with the question and often the knoledge base gets cleaned up when the answer is more basic.

You have one of the most contagous smiles I have ever seen. I look foward to your posts because of it. I also enjoy your enthusiastic approach to things.

Thank you, Vance
 

dabkb2

Dave Bacon
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I think Tina and I will leave it like it is for now, it seems to start and run very well. Mabea the centrifugle advance might work beter, but as long as the motor has enough power and does not get any hotter than 180 and does not ping I think it will be fine.

thanks for all the great info ,we'll let you know how it goes this weekend, as Tina is going for her lessons, Charlie Mara said he would fly the gyro to make sure it is all good. More to come later
 

Paul_Zurawski

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I have the points ignition, with the vacuum advance hooked up on my EA-81. The engine starts on the first flip of the prop, and doesnt miss or lack power. I get 3600rpm at full power. Since there are so many combinations of engine systems put together, you have to do what works with your setup.
 

Butch S.

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15* @ distributor Which = 30* @ the cank & I can say tina DO NOT RECONECT THE VAC ADVANCE because a ea81 wont make more power with more advance than 35* btdc I know I'v paid for the dyno time
SO lets do our homework and some math
base setting 10* + 30*= 40* 5* to much now add vac advance 10* = 50*
this is detonation [knock] heaven
I now regaph my dizzys to only have 9*-10* of advance ths probably wont help with prop starting
but I did prop start with this set up & a flat battery a while ago
Butch S.
 

Paul_Zurawski

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When you say more power, are you talking about engine RPM? In flight, I am getting 3600 rpm on a Tenn 52-26 prop. If you think I can get any more rpm, I will look at resetting the timing without the advance hooked up.
 

dabkb2

Dave Bacon
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paul

paul

Tina was a 52 26 tennese prop and a hand held rpm read 3400, is that enough?
 

Paul_Zurawski

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My gyro weighs 400lbs empty, and I am 200lbs. On a cool day, 50F, I will climb about 400fpm...warm 85f...about 250-300fpm. I am sure she doesnt weigh 200lbs, so that power should be okay. My static rpm is just under 3600, and in cruise, I get right at 3600rpm.
 
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